Composition for microstructured screens

ABSTRACT

A composition having at least about 10 percent perfluoroalkylsulfonamideoethyl acrylate; at least about 5 percent aliphatic urethane acrylate oligomer; at least about 1 percent acrylate monomer; and less than about 84 percent other reactive and non-reactive components. The composition, with the addition of a light absorbing pigment, is particularly useful as a light absorbing adhesive in an optical element such as a rear projection screen that incorporates totally internally reflecting structures to disperse the light passing through the screen.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/733,479, filed Dec. 11, 2003.

This application incorporates by reference co-pending applications Ser.No. 10/733,066, filed Dec. 11, 2003, entitled “Microstructured Screenwith Light Absorbing Material and Method of Manufacturing,” by PatrickA. Thomas et al. and Ser. No. 10/732,993, filed Dec. 11, 2003, entitled“Microstructured Screen and Method of Manufacturing Using Coextrusion,”by Kathryn M. Spurgeon et al.

BACKGROUND OF THE INVENTION

The present invention is directed generally to a composition for use inmanufacturing a rear projection screen and the resulting screen, andmore particularly to a rear projection screen that incorporates totallyinternally reflecting structures to disperse the light passing throughthe screen.

Rear projection screens are generally designed to transmit an imageprojected onto the rear of the screen into a viewing space. The viewingspace of the projection system may be relatively large (e.g., rearprojection televisions), or relatively small (e.g., rear projection datamonitors). The performance of a rear projection screen can be describedin terms of various characteristics of the screen. Typical screencharacteristics used to describe a screen's performance include gain,viewing angle, resolution, contrast, the presence of undesirableartifacts such as color and speckle, and the like.

It is generally desirable to have a rear projection screen that has highresolution, high contrast and a large gain. It is also desirable thatthe screen spread the light over a large viewing space. Unfortunately,as one screen characteristic is improved, one or more other screencharacteristics often degrade. For example, the horizontal viewing anglemay be changed in order to accommodate viewers positioned at a widerange of positions relative to the screen. However, increasing thehorizontal viewing angle may also result in increasing the verticalviewing angle beyond what is necessary for the particular application,and so the overall screen gain is reduced. As a result, certaintradeoffs are made in screen characteristics and performance in order toproduce a screen that has acceptable overall performance for theparticular rear projection display application.

In U.S. Pat. No. 6,417,966, incorporated herein by reference,Moshrefzadeh et al. disclose a screen having reflecting surfacesdisposed so as to reflect light passing therethrough into at least onedispersion plane. The screen thereby permits asymmetric dispersion ofimage light in a rear projection system and allows the light to beselectively directed towards the viewer. Moshrefzadeh et al. also teachmethods for manufacturing the screen, including combinations of stepsusing casting and curing processes, coating techniques, planarizationmethods, and removing overcoating materials.

BRIEF SUMMARY OF THE INVENTION

The present invention is a composition having at least about 10 percentperfluoroalkylsulfonamideoethyl acrylate; at least about 5 percentaliphatic urethane acrylate oligomer; at least about 1 percent acrylatemonomer; and less than about 84 percent other reactive and non-reactivecomponents. The composition, with the addition of a light absorbingpigment, is particularly useful as a light absorbing adhesive in anoptical element such as a rear projection screen that incorporatestotally internally reflecting structures to disperse the light passingthrough the screen.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be further explained with references to thedrawing figures below, wherein like structure is referred to by likenumerals throughout the several views.

FIG. 1 is a side elevation view of a microrib screen structure.

FIG. 2 is a side elevation view of the structure of FIG. 1 filled withlight-absorbing material.

FIG. 3 is a diagram of one embodiment of a method for producing thestructure of FIG. 1.

FIG. 4 illustrates the structure of FIG. 2 with additional layers.

FIG. 5 is a diagram illustrating one embodiment of a method forproducing the structure of FIG. 4.

FIG. 6 is a side elevation diagram of a step of a method for producing astructure using a composition of the present invention.

FIG. 7A is a side elevation view of one embodiment of a screen producedby the method of FIG. 6.

FIG. 7B is a side elevation view of a second embodiment of a screenproduced by the method of FIG. 6.

FIG. 8 is a graph illustrating screen performance based on a variety ofblack adhesive composition formulations of the present invention.

FIG. 9 illustrates yet another method by which a screen may bemanufactured.

FIGS. 10A-10C illustrate steps for manufacturing a screen in anothermethod.

FIG. 10D illustrates an alternate step in a method for producing a rearprojection screen element.

FIG. 11 illustrates a third embodiment of a rear projection screen.

FIG. 12 is a side elevation view of a fourth embodiment of a rearprojection screen.

While the above-identified drawing figures set forth several embodimentsof the invention, other embodiments are also contemplated. Thisdisclosure presents illustrative embodiments of the present invention byway of representation and not limitation. Numerous other modificationsand embodiments can be devised by those skilled in the art which fallwithin the scope and spirit of the principles of this invention. Thedrawing figures are not drawn to scale.

Moreover, while some embodiments are referred to by the designations“first,” “second,” “third,” etc., it is to be understood that thesedescriptions are bestowed for convenience of reference and do not implyan order of preference. The designations are presented merely todistinguish between different embodiments for purposes of clarity.

DETAILED DESCRIPTION

FIG. 1 is a side elevation view of a microrib screen structure.Variations of the illustrated embodiments can be utilized for frontprojection and other screen applications, but they will be describedprimarily with reference to rear projection screen applications for thepurposes of this disclosure. Microrib structure 20 includes a lighttransmitting base substrate 22 and microstructured diffusive ribs 24.The term “microstructured” includes features having characteristicdimensions measured in micrometers (μm) or smaller units. In general,microstructured features may have characteristic dimensions ranging fromless than 0.01 μm to more than 100 μm. What constitutes a characteristicdimension of a feature depends on the type of feature. Examples includethe width of trough-like features in a surface, the height of post-likeprotrusions on a surface, and the radius of curvature at the point ofsharp protrusions or indentions on a surface. Thus, even a macroscopicfeature can be said to be microstructured if a characteristic dimensionof the feature has dimensions with sub-micrometer tolerances. In a firstembodiment, base substrate 22 is a light transmitting film of a materialsuch as a polymer.

In one exemplary embodiment, linear ribs or microribs 24 are formed ofan optical-grade host material such as a resin; in particular, the resinincorporates light scattering particles such as beads so that ribs 24act as a bulk diffuser. A sufficiently high aspect ratio is chosen forthe rib geometry in order to induce total internal reflection (TIR) inthe microrib structure 20. In the embodiment shown in FIG. 1, the lightdiffusive ribs 24 are separated by V-shaped cavities or grooves 26.While light diffusive structures 24 are described in an exemplaryembodiment as ribs that extend across substantially the entire width ofbase substrate 22, it is also contemplated that the structures 24, in analternative embodiment, form discrete peaks that can be arranged uponbase substrate 22 in a staggered, or “checkerboard” pattern, forexample. In an exemplary embodiment, each structure 24 has a base 23 anda plurality of walls 25 which narrow the structure 24 as walls 25 extendfrom base 23.

A material such as a resin with a high refractive index (RI) isgenerally chosen for diffusive ribs 24. In this application, the RI of arib 24 refers to the RI of the host material. Examples of suitable hostmaterials for light diffusive ribs 24 include polymers such as modifiedacrylics, polycarbonate, polystyrene, polyester, polyolefin,polypropylene, and other optical polymers preferably having a refractiveindex equal to or greater than about 1.50.

FIG. 2 is a side elevation view of the structure of FIG. 1 filled withlight-absorbing material 28. Embedded microstructured film 27 includesfilling material 28. Material 28 typically incorporates a black pigmentor dye to absorb ambient light and improve contrast in the final screenconstruction. Optical material 28 has a low refractive index so that arelatively high difference in refractive index exists between lightabsorbing material 28 and the material composing light diffusive ribs24. A refractive index difference of at least about 0.06 is desired.Such a difference induces efficient internal reflection and high screenperformance. Internally reflecting surfaces 29 are formed by theinterfaces between light diffusive ribs 24 and light absorbing material28. In one exemplary embodiment, front surface 30 of embeddedmicrostructured film 27 is a smooth or slightly matte surface withminimal land on the rib top surfaces 31. Totally internally reflectingsurfaces 29 disperse light through optically transmitting areas 31 offront surface 30. Front surface 30 preferably has a matte surface finishthat assists in scattering the light propagating therethrough.

In a first embodiment, light absorbing material 28 includes about 20% toabout 50% (preferably about 39%) propoxylated neopentyl glycoldiacrylate from Sartomer Company; about 50% to about 80% (preferablyabout 58%) proprietary RC-709 acrylated silicone from GoldschmidtChemical; about 1% to about 3% (preferably about 2%)2-hydroxy-2-methyl-1-phenyl-1-propanone photoinitiator; and about 1%lampblack dispersion (the lampblack dispersion contains about 67.5%tetrahydrofurfuryl acrylate from Sartomer Company; about 25% LB 1011lampblack carbon black from Elementis Pigments; and about 7.5% EFKA 4046(dried) from Lubrizol).

The propoxylated neopentyl glycol diacrylate increases adhesion toadhesive 64 (see FIG. 5) and has desirable toughness, flexibility, andlow shrinkage properties; however, too much propoxylated neopentylglycol diacrylate increases the RI of light absorbing material 28, whichis not desirable. The RC-709 acrylated silicone from GoldschmidtChemical desirably decreases RI; however, too much of it decreasesadhesion to adhesive 64. The percentage of lampblack dispersion isdictated by the total concentration of carbon black that is desired inthe total formulation, in this case about 3,000 ppm (parts per million).The use of EFKA 4046 in the lampblack dispersion is key to maintaining adispersion of carbon black parties in the material 28 formulation forextended periods of time. Carbon black is not inherently compatible withacrylated silicone and will flocculate and settle when mixed withacrylated silicone without a dispersion agent.

To obtain a stable material 28 resin, the order of mixing components isimportant. In one embodiment, dried EFKA 4046 is obtained by firstadding an approximate 4:1 ratio of heptane or hexane to the EFKA 4046(the EFKA 4046 is dissolved in ethyl acetate from the supplier). TheEFKA 4046 will precipitate out of solution and settle to the bottom ofthe container. The liquid is decanted and discarded. The wet solids arespread in a pan in a thickness of less than 1.27 cm (0.5 inch). The panis placed in an oven at about 65.6 E C (150 E F) for about 24 to about36 hours. The dried solids are then broken into small pieces for use.The lampblack dispersion is prepared by dissolving dried EFKA 4046 intotetrahydrofurfuryl acrylate; carbon black is added to the solution in aball mill and mixed for about one hour. The lampblack dispersion ismixed with the propoxylated neopentyl glycol diacrylate with a highshear rotor-stator mixer to wet out the carbon black particles. Then theacrylated silicone and photoinitiator are added.

Adhesion between light absorbing material 28 and adhesive 64 may beenhanced by modification of front surface 30 by treatment, such as withcorona discharge (including nitrogen or air corona treatments), plasma,priming, or using a tie layer. In one embodiment, a clear tie layer ofnon-silicone, cured acrylate is used to provide a bonding surface foradhesive 64.

FIG. 3 is a diagram of one embodiment of a method for producing thestructure of FIG. 1. A process for producing the screen structure 27 ofFIG. 2 includes a microreplication process 32 to produce diffusive ribs24 on base substrate 22 and a planarization process 34 to coat lightabsorbing material 28 onto the microrib structure 20 to form embeddedmicrostructured film 27. The term “microreplication” includes a processwhereby microstructured features are imparted from a master or a moldonto an article. The master is provided with a microstructure, forexample by micro-machining techniques such as diamond turning, laserablation or photolithography. The surface or surfaces of the masterhaving the microstructure may be covered with a hardenable material sothat when the material is hardened, an article is formed that has anegative replica of the desired microstructured features. Themicroreplication may be accomplished using rolls, belts, and otherapparatuses known in the art. Microreplication can be accomplished bytechniques including but not limited to extruding, embossing, radiationcuring and injection molding. Microreplication process 32 uses substrateunwind station 36, resin coating station 38, precision nip roll 40,microstructured cylinder 42, ultraviolet lamp 44 and precision nip roll46. Planarization process 34 uses resin coating station 48, precisionnip roll 50, a smooth, matte or microstructured cylinder 52, ultravioletlamp 54, precision nip roll 56 and embedded microstructured film rewind58.

In one embodiment, the microreplication process 32 and planarizationprocess 34 are performed in sequence. Base substrate 22 is first unwoundfrom substrate unwind station 36. Base substrate 22 is guided to passinto microreplication process 32 resin coating station 38, where thebase is coated with a high refractive index resin incorporating lightscattering particles. The base substrate 22 and light diffusive materialcoating are pressed by precision nip roll 40 against microstructuredcylinder 42 to impart the ribbed structure to the light diffusivematerial. The cast structure is then cured by light from ultravioletlamp 44 and microribbed structure 20 emerges from precision nip roll 46,resulting in the monolithic structure illustrated in FIG. 1.

Microrib structure 20 continues on to resin coating station 48, where itis overcoated with light absorbing material 28. The composite structureis pressed by precision nip roll 50 against cylinder 52. Cylinder 52 maybe smooth, matte or microstructured to impart a desired texture uponfront surface 30 of the resulting embedded planar microstructured film27 shown in FIG. 2. After light absorbing material 28 is cast ontomicrorib structure 20, the film proceeds to be cured by light fromultraviolet lamp 54. A completed embedded microstructured film 27emerges from precision nip roll 56 to be wound upon embeddedmicrostructured film rewind 58. FIG. 4 illustrates the structure of FIG.2 with additional layers: Shielded screen 60 incorporates embeddedmicrostructured film 27 with back surface 62 and adhesive 64 on frontsurface 30 for the attachment of a light transmitting shield 66. Shield66 is a protective layer that can be a film or sheet made of transparentmaterial such as acrylic, polycarbonate or glass, for example. Shield 66functions as a protective element so that the coated microstructuredfilm 27 is not damaged by contact. Shield 66 is an optional component,though most applications benefit greatly from this protection. Shield 66can be made to be anti-glare (matte), anti-reflective, anti-static,anti-scratch or smudge resistant, for example, through coatings, surfacetextures, or other means. In one embodiment, shield 66 is a 3 millimeterthick acrylic panel from Cyro Industries with a non-glare, matteoutward-facing surface.

The thickness of base film 22 can be chosen to meet the requirements ofeach particular application. For example, a thin base film with athickness of about 0.127 mm (5 mils) to about 0.254 mm (10 mils) can bechosen to provide for ease of manufacturing; alternatively, a thick filmwith a thickness of about 0.508 mm (20 mils) to about 1.016 mm (40 mils)can be chosen to provide additional product stiffness. Suitablematerials include polycarbonate, polyester, acrylic, polyolefin,polypropylene and vinyl films, for example. In one exemplary embodiment,back surface 92 of base substrate 22 has a matte finish to reducespecular reflection back into the imaging system.

Shield 66 can also be varied to provide for different functionalities.Shield 66 can range in thickness from thin (less than about 0.508 mm (20mils)) to semi-rigid (about 0.508 mm (20 mils) to about 1.016 mm (40mils)) to rigid (greater than about 1.016 mm (40 mils)). The thicknessof base substrate 22 and protective shield 66 can be chosen to yield awide variety of products with these options impacting total materialcost, optical functionality, overall construction stiffness and ease ofprocessing.

FIG. 5 is a diagram illustrating one embodiment of a method forproducing the structure of FIG. 4. In one embodiment, lamination process68 directly follows planarization process 34 in a single assemblyprocess. Lamination process 68 uses adhesive unwind 70, lamination nipassembly 72 and lamination nip assembly 74. Either of lamination nipassemblies 72 or 74 may be driven, or separate drive wheels or otherdrive mechanisms can be used to propel components through process 68.The adhesive material disposed on adhesive unwind 70 is typically alayer of pressure-sensitive adhesive sandwiched between two linerlayers. When the adhesive material is unwound from adhesive unwind 70,top liner 76 is separated therefrom and wound upon top liner rewind 78.The remaining adhesive material 80 is contacted with embeddedmicrostructured film 27, which is unwound from film unwind 58. Embeddedmicrostructured film 27 and adhesive material 80 pass through laminationnip 72, where they are pressed together.

Thereafter, bottom liner 82 of the adhesive composite 80 is removed andwound onto bottom liner rewind 84. A shield 66 is introduced on atransversely traveling feed web or other suitable mechanism and disposedonto the exposed adhesive 64. The structure then passes throughlamination nip 74, where shield 66 is pressed onto microstructured film27 and adhered thereto by adhesive 64. The embedded microstructured film27 can be severed between discrete shields 66 to form individualshielded screens 60. However, the lamination process can add significantcost to the overall product due to slow line speed, added yield cost,and material utilization. For example, use of the optical qualitypressure-sensitive adhesive 64 is very expensive and leads to waste inthe form of top liner 76 and bottom 82.

FIG. 6 illustrates an alternate method for forming shielded screen 60which eliminates various steps and materials used in the methods ofFIGS. 3 and 5. FIG. 6 is a side elevation diagram of a step of a secondmethod. In one embodiment, microrib structure 20 is formed by themicroreplication process 32 discussed above with respect to FIG. 3 toimpart light diffusive ribs 24 having V-shaped grooves 26 onto basestructure 22. An alternate process illustrated in FIG. 6 eliminates theplanarization process 34 shown in FIG. 3 and the two-step laminationprocess shown in FIG. 5 by introducing a light absorbing adhesive 86 ofthe present invention which replaces both light absorbing material 28and adhesive 64. By combining the light absorption and adhesivefunctions in one material, savings in materials and manufacturing stepsare obtained. Light absorbing adhesive 86 is disposed on rear surface 87of shield 66. Shield 66, with light absorbing adhesive 86 disposedthereon, is brought together with microrib structure 20. As shown byarrow 89, for example, shield 66 and microrib structure 20 are laminatedtogether.

It is typically desirable for shielded screen 60 to be relatively rigid(see FIG. 5). Because thinner substrates 22 are typically used, rigidshields 66 are normally selected to yield a rigid shielded screen 60.However, rigid materials must be pre-sheeted and fed into the laminationprocess 68 shown in FIG. 5, making the process 68 semi-continuous andresulting in lower process rates. The process shown in FIG. 6 can usethicker but flexible substrates 22 and shields 66. This lamination offlexible substrates 22 and flexible shields 66 with light absorbingadhesive 86 into a rigid shielded screen can be achieved in a continuousprocess in excess of 20 feet per minute. After lamination, an in-linecutter can be used to sever the laminated product into individual rigidshielded screens.

As an example, a 1.27 mm (50 mil) composite shielded screen made by theprocess of FIG. 6 with a 0.508 mm (20 mil) substrate 22, a 0.254 mm (10mil) layer of diffusive ribs 24 filled with light absorbing adhesive 86,and a 0.508 mm (20 mil) shield 66 is as stiff or stiffer than amulti-layer Toppan screen at 1.524 mm (60 mils) and is significantlystiffer than a DNP mono-layer screen at 1.27 mm (50 mils). The addedstiffness is attributable to the adhesive nature of light absorbingadhesive 86.

In one exemplary embodiment, light absorbing adhesive 86 is aphotopolymerizable, low refractive index material which adheres to bothlight diffusive ribs 24 and shield 66. In an exemplary embodiment, therefractive indices of light diffusive ribs 24 and light absorbingadhesive 86 differ enough to cause total reflection rather thantransmittance at the interface therebetween. In an exemplary embodiment,the refractive index of the microrib material of light diffusive ribs 24varies from 1.49 for simple acrylate materials to 1.58 or higher formaterials such as aromatic polycarbonates. The refractive indexrequirement for the groove filler material 86 is, therefore, dependenton the optical properties (such as refractive index) of the microrib 24material. For the high refractive index microrib materials, such aspolycarbonate, commercially available photolaminating adhesives may beadequate. Exemplary adhesives 86 have a RI of less than about 1.50.Particularly suitable adhesives 86 have a RI of less than about 1.45.

In some embodiments, adhesive 86 is a pigmented blend of one or more ofthe following components: urethane acrylate oligomers; substitutedacrylate, diacrylate, and triacrylate monomers; fluorinated acrylatesincluding perfluoroalkylsulfonamidoalkyl acrylates; fluorinatedacrylamides; acrylated silicones; acrylated silicone polyureas and UV orvisible light activated photoinitiators. Perfluoroalkylsulfonamidoalkylacrylates are particularly useful due to low RI and good mechanicalproperties. Suitable components are described in U.S. patent applicationPublications Nos. U.S. 2003/0139549 and U.S. 2003/0139550; bothincorporated herein by reference; both by Patricia M. Savu et al.; bothentitled “Fluorochemical Sulfonamide Surfactants;” filed on Oct. 4, 2002and Dec. 5, 2002, respectively; and both published on Jul. 24, 2003.

If the viscosity of the groove filler 86 is too low, it will flow duringthe groove filling process. This can waste material, give nonuniformthickness, and contaminate the process equipment. If the viscosity istoo high, filling the grooves 24 can be a slow, difficult process andthe possibility of introducing bubbles (optical defects) increasessignificantly. While photolamination can be accomplished with fluidshaving viscosities as low as about 150 centipoises, many processes canbenefit from a viscosity of at least about 400 centipoises beforepolymerization. While viscosities as high as about 5,000 centipoisesbefore polymerization can be used, viscosities no higher than about1,500 centipoises before polymerization are especially suitable forreasonable process speed and bubble-free coatings.

A standard measure of adhesion between substrates and coatings is theamount of force required to separate them, known as the peel force. Thepeel force of a system containing excellent interfacial adhesion at theinterface between layers will be very high. While peel force strength ofat least about 35.7 kg/m (2 pounds/inch) is probably adequate betweendiffusive ribs 24 and light absorbing adhesive 86, it is more desirableto have peel force of at least about 71.4 kg/m (4 pounds/inch). Thishigh peel force should be maintained under environmental test conditionsof high temperature and humidity. Adequate adhesion may be achieved bymodification of the substrate surfaces by treatment, such as with coronadischarge (including nitrogen or air corona treatments), plasma,priming, or using a tie layer. It is preferred, however, that theadhesive 86 adhere to the light diffusive ribs 24 and shield 66, ifused, without the necessity of surface modification.

One suitable embodiment of light absorbing adhesive 86 is constructed bywarming the following resin components to about 70 EC (158 EF) to lowerthe viscosity sufficiently to allow for agitation: 16.0 g aliphaticurethane acrylate oligomer; 19.0 g ethoxyethoxyethyl acrylate; 5.5 ghexanediol diacrylate; 5.0 g tetrahydrofurfuryl acrylate; 44.5 gN-methyl-perfluorobutylsulfonamidoethyl acrylate; 10.0 gacryloyloxyethoxyperfluorobutane; and 1.0 g phenyl bis(2,4,6 trimethylbenzoyl) phosphine oxide photoinitiator.

The components are then shaken until a clear solution results. Thesolution is then pigmented for light absorption. One suitable pigment iscarbon black; in one embodiment, the pigment is used in a concentrationbetween about 50 ppm and about 20,000 ppm; in one exemplary embodiment,the pigment is used in a concentration greater than about 1000 ppm andless than about 9000 ppm. A concentration of about 3000 ppm isparticularly suitable, based on mass ratios of the carbon black materialto the resin material. In one embodiment, the formulation is disposedonto shield 66 by a conventional method such as knife coating. Thecoated shield is then pressed onto microrib structure 20 as shown inFIG. 6, for example, to partially or completely fill grooves 26. Excessadhesive 86, if any, is expelled by running a rubber roller over theconstruction. The construction is passed under a 11.81 W/mm (300Watt/in). Fusion Systems D lamp one or more times at about 6.1 m (20feet) per minute. In an alternate method, the formulation may be coateddirectly onto the microrib structure 20, and shield 66 then adhered tothe microrib structure 20 with adhesive 86 already disposed thereon.Thereafter, the steps of removing excess adhesive 86 and curing theconstruction are the same as discussed above.

FIG. 7A is a side elevation view of one embodiment of a screen producedby the method of FIG. 6. The step of FIG. 6 can result in a completelyfilled structure illustrated at FIG. 7A. In one exemplary embodiment,light absorbing adhesive 86 has a low refractive index to produceefficient TIR within ribs 24. Light absorbing adhesive 86 is formulatedto effectively bond diffuser ribs 24 to shield 66. Light absorbingadhesive 86 can possess low shrinkage properties to produce acosmetically acceptable lamination result. Moreover, it is particularlysuited that light absorbing adhesive 86 is curable by ultraviolet lightin order to allow for convenient processing and a fast cure.

In one embodiment, light diffusive ribs 24 are replicated from a toolingmold using a high refractive index diffuser resin, as shown inmicroreplication process 32 of FIG. 3. In this application, allpercentages are by mass unless otherwise indicated. One suitable resinis about 79% aliphatic urethane acrylate oligomer, about 19%2-phenoxyethyl acrylate, and about 2%2-hydroxy-2-methyl-1-phenyl-1-propanone photoinitiator. Another suitableresin is about 69% aliphatic urethane acrylate oligomer, about 29%2-(1-naphthyloxy)-ethyl acrylate, and about 2%2-hydroxy-2-methyl-1-phenyl-1-propanone photoinitiator. The resin forforming ribs 24 is coated from resin coating station 38 onto substrateor base structure 22. Base structure 22 with resin thereon is molded bymicrostructured cylinder 42 and cured by ultraviolet (UV) lamps orelectron beams 44. Typical UV cure conditions use a 23.62 W/mm (600Watt/in) Fusion Systems D bulb system, operated at belt speeds of about3.05 m (10 feet) to about 6.10 m (20 feet) per minute, with one or morepasses under the UV bulb. The formed microrib structure 20 is removedfrom microreplication process 32, yielding a self-supporting structure.

Then, a pigmented, typically black, light absorbing adhesive 86 isapplied to a second substrate such as shield 66. One suitable lightabsorbing adhesive 86 is formed from a resin having about 30%“Formulation A,” (the “Formulation A” having about 38.5% aliphaticurethane acrylate oligomer; about 26.9% ethoxyethoxyethyl acrylate;about 28.8% isobomyl acrylate; about 5.8% hexanediol diacrylate; andabout 1% ∀,∀-diethoxyacetophenone (DEAP) photoinitiator); about 10%aliphatic urethane diacrylate; about 30% trifluoroethyl acrylate; andabout 30% N-methyl-perfluorobutylsulfonamidoethyl acrylate. Anothersuitable light absorbing material 86 is formed from a resin having about50% “Formulation A,” discussed above, and about 50%N-methyl-perfluorobutylsulfonamidoethyl acrylate. In one exemplaryembodiment, light absorbing adhesive 86 contains a pigment such ascarbon black. In one embodiment, the pigment is used in a concentrationbetween about 50 ppm (parts per million) and about 20,000 ppm. In oneexemplary embodiment, the pigment is used in a concentration greaterthan about 1,000 ppm and less than about 9,000 ppm. A concentration ofabout 3,000 ppm is particularly suitable, based on mass ratios of thecarbon black material to the adhesive material.

Light absorbing adhesive 86 can be applied to a second substrate such asshield 66 in sufficient quantity to completely fill diffuser ribs 24,allowing a slight excess to ensure complete fill, in the laminationmethod illustrated in FIG. 6. The excess adhesive squeezes out ofcompletely filled structure 88 upon lamination. Completely filledstructure 88 is then exposed to radiation under conditions similar tothose discussed above for microreplication process 32. The exposure can,for example, result in a partial or complete polymerization of thematerial. After at least partial polymerization, light absorbingadhesive 86 is a copolymer of its components.

FIG. 7B is a side elevation view of another embodiment of a screenproduced by the method of FIG. 6. When a small thickness or amount oflight absorbing adhesive 86 is used in the step illustrated in FIG. 6,partially filled structure 90 results. In partially filled structure 90,air gaps 94 are left in V-shaped grooves 26. A benefit of air gap 94 isthat low refractive index air fills the rib grooves 26 and creates alarge refractive index difference between the grooves 26 and the lightdiffusive ribs 24, further enhancing “TIR efficiency.” Because therefractive index of air is 1.0, the difference in refractive indexbetween air gap 94 and light diffusive ribs 24 is usually greater thanabout 0.5. Because air gap 94 creates the bulk of the diffuser ribinterface, light absorbing adhesive 86 need not possess as low arefractive index as when the ribs are completely filled in structure 88.This allows for the selection of an adhesive 86 to optimize otherimportant properties, such as low shrinkage and high peel strengthadhesion, for example. Since the adhesive contact area between lightabsorbing adhesive 86 and diffuser ribs 24 is smaller, light absorbingadhesive 86 may possess greater adhesion properties in partially filledstructure 90 than completely filled structure 88.

In both completely filled structure 88 and partially filled structure90, the level of light absorbing material used in light absorbingadhesive 86 is chosen based on the desired amount of contrastenhancement and ambient light absorption. The light absorbing materialin an exemplary embodiment is a black pigment such as carbon black. Incompletely filled structure 88, the black pigment concentration can berelatively low and yet yield an acceptable total fixed absorbance, oroptical density value, because the thickness of the layer of lightabsorbing adhesive 86 is large. A suitable loading concentration ofpigment such as carbon black in completely filled structure 88 in oneembodiment is between about 50 ppm (parts per million) and about 20,000ppm. In an exemplary embodiment, the concentration is greater than about1000 ppm and less than about 9000 ppm. A concentration of about 3000 ppmis particularly suitable, based on mass ratios of the carbon blackmaterial to the adhesive material. However, in partially filledstructure 90, the coating thickness is small; therefore, the blackpigment concentration must be larger to yield the same optical density.In the latter case, the ambient light absorption is larger per unit ofcoating thickness than in the former case. A suitable loadingconcentration of pigment such as carbon black in partially filledstructure 90 in one embodiment is between about 50 ppm and about 20,000ppm. In an exemplary embodiment, the concentration is greater than about5,000 ppm and less than about 10,000 ppm, based on mass ratios of thecarbon black material to the adhesive material.

A challenge in both completely filled structure 88 and partially filledstructure 90 is the removal of excess adhesive 86 from front surface 30of diffuser ribs 24 during lamination. If all of the light absorbingadhesive 86 is not removed from front surface 30 of the diffuser ribs 24during lamination, some image light can be lost due to absorption duringTIR transmission. In a partially filled structure 90 with more highlypigmented adhesive 86, more loss of image light can occur for the sameresidual black layer thickness.

FIG. 8 is a graph illustrating screen performance based on a variety ofblack adhesive formulations. One way of gauging screen performance is byplotting the horizontal gain curve as a function of viewing angle. Theplotted curves describe the brightness of the screen perceived by aviewer as the viewer moves sideways away from the center of the screen.“TIR efficiency” relates to the range of incident light angles thatresult in total internal reflection; the greater the range, the higherthe efficiency. TIR efficiency increases as the difference in refractiveindex increases between light absorbing adhesive 86 and diffusive ribs24. Reflection from the rib 24 sides can produce a local maximum in thegain curve as shown. As both the TIR efficiency and RI differenceincrease, the secondary peak in the gain curve (near 30 degreeshorizontal viewing angle) can increase. The effect of a local maximumcan be reduced or eliminated by, for example, introducing lightdiffusion into the projection screen. For example, ribs 24 may includeparticles to make the local maximum less pronounced by scattering anyincident light.

Curve 96 refers to a benchmark standard screen of constructionillustrated in FIG. 4. The benchmark standard screen has light diffusiveribs 24 formed from a resin having about 80% aliphatic urethane acrylateoligomer and about 20% 2-phenoxyethyl acrylate. Light diffusive ribs 24have a refractive index of about 1.51. Light absorbing material 28 isformed from a resin having about 60% proprietary RC709 silicone acrylatefrom Goldschmidt Corp., about 39% propoxylated neopentyl glycoldiacrylate, and about 1% Darocur 4265 (a 1:1 blend of2-hydroxy-2-methyl-1-phenyl-1-propanone and diphenyl(2,4,6-trimethylbenzoyl)-phosphine oxide) photoinitiator with carbonblack pigment in a concentration of about 3,000 ppm. Light absorbingmaterial 28 has a refractive index of about 1.45. The RI differencebetween light absorbing material 28 and light diffusive ribs 24 is about0.06. This formulation of light absorbing material 28 possesses lowshrinkage characteristics, good processing properties, uniformdispersion of the black pigment, low price and widespread availability.

Curve 98 refers to a screen formed by the method illustrated in FIGS. 6and 7A which shows the gain when the RI difference between diffuser ribs24 and light absorbing adhesive 86 is less than about 0.01. The screencorresponding to curve 98 has light diffusive ribs 24 formed from aresin having about 80% aliphatic urethane acrylate oligomer and about20% 2-phenoxyethyl acrylate. Light diffusive ribs 24 have a refractiveindex of about 1.51. Light absorbing material 28 is formed from a“Formulation A” resin having about 38.5% aliphatic urethane acrylateoligomer; about 26.9% ethoxyethoxyethyl acrylate; about 28.8% isobomylacrylate; about 5.8% hexanediol diacrylate; and less than about 1%∀,∀-diethoxyacetophenone (DEAP) photoinitiator. Light absorbing material28 has a refractive index of about 1.50.

Curve 100 refers to a screen formed by the method illustrated in FIGS. 6and 7A which has increased “TIR efficiency” when a light absorbingadhesive 86 with relatively low RI is used. The screen corresponding tocurve 100 has light diffusive ribs 24 formed from a resin having about80% aliphatic urethane acrylate oligomer and about 20% 2-phenoxyethylacrylate. Light diffusive ribs 24 have a refractive index of about 1.51.Light absorbing material 28 is formed from a resin having about 30%“Formulation A,” discussed above; about 10% aliphatic urethanediacrylate; about 30% trifluoroethyl acrylate; about 30%N-methyl-perfluorobutylsulfonamidoethyl acrylate; and about 1%∀,∀-diethoxyacetophenone (DEAP) photoinitiator. Light absorbing material28 has a refractive index of about 1.44.

Finally, curve 102 refers to a screen formed by the method illustratedin FIGS. 6 and 7A, in which the TIR efficiency is increased, where theRI difference between light absorbing adhesive 86 and light diffusiveribs 24 is about 0.08. The screen corresponding to curve 102 has lightdiffusive ribs 24 formed from a resin having about 70% aliphaticurethane acrylate oligomer and about 30% 2-(1-naphthyloxy)-ethylacrylate. Light diffusive ribs 24 have a refractive index of about 1.53.Light absorbing material 28 is formed from a resin having about 50%“Formulation A,” discussed above; about 50%N-methyl-perfluorobutylsulfonamidoethyl acrylate; and about 1%∀,∀-diethoxyacetophenone (DEAP) photoinitiator. Light absorbing material28 has a refractive index of about 1.45.

As shown in FIG. 8, the formulation of light absorbing adhesive 86relative to the formulation of light diffusive ribs 24 can be chosen toproduce the desired screen performance characteristics. Usually, theformulations are chosen to maximize the RI difference between lightabsorbing adhesive 86 and light diffusive ribs 24. It is desirable forlight absorbing adhesive 86 to achieve strong adhesion to lightdiffusive ribs 24 and protective shield 66, possess a relatively low RI,have high mechanical strength after curing, and processabilityproperties such as appropriate viscosity and curability by ultravioletlight. A suitable component of light absorbing material 86 is analiphatic urethane acrylate oligomer. In some embodiments, lightabsorbing adhesive 86 contains at least about 5 percent of an aliphaticurethane acrylate oligomer. In an exemplary embodiment, light absorbingadhesive 86 contains at least about 10 percent of an aliphatic urethaneacrylate oligomer. In some embodiments, light absorbing adhesive 86contains less than about 50 percent of an aliphatic urethane acrylateoligomer. In an exemplary embodiment, light absorbing adhesive 86contains less than about 40 percent of an aliphatic urethane acrylateoligomer. If the concentration of aliphatic urethane acrylate oligomeris too low, light absorbing adhesive 86 may not be viscous enough; ifthe concentration is too high, light absorbing adhesive 86 may be tooviscous, and the refractive index may be too high.

Another suitable component of light absorbing material 86 is a low RIcompatible acrylate monomer, of which ethoxyethoxyethyl acrylate is anexample. In some embodiments, light absorbing adhesive 86 contains atleast about 1 percent of an acrylate monomer. In an exemplaryembodiment, light absorbing adhesive 86 contains at least about 8percent of an acrylate monomer. In some embodiments, light absorbingadhesive 86 contains less than about 30 percent of an acrylate monomer.In an exemplary embodiment, light absorbing adhesive 86 contains lessthan about 20 percent of an acrylate monomer. In an exemplaryembodiment, the acrylate monomer has a relatively low RI and serves as asolvent to enhance the compatibility of the other components of lightabsorbing adhesive 86. Other suitable acrylate monomers include, forexample, fluorinated acrylates such as trifluoroethyl acrylate,perfluoroalkanoamidoalkyl acrylate and perfluorobutyramidoethylacrylate.

Another suitable component of light absorbing material 86 is amultifunctional acrylate monomer to add strength, of which hexanedioldiacrylate is an example. In some embodiments, light absorbing adhesive86 contains at least about 0.1 percent of a multifunctional acrylatemonomer. In an exemplary embodiment, light absorbing adhesive 86contains at least about 1.0 percent of a multifunctional acrylatemonomer. In some embodiments, light absorbing adhesive 86 contains lessthan about 10 percent of a multifunctional acrylate monomer. In anexemplary embodiment, light absorbing adhesive 86 contains less thanabout 6 percent of a multifunctional acrylate monomer. The higher thefunctionality of the multifunctional acrylate monomer, the lower therequired concentration.

The screen with “Formulation A” light absorbing adhesive 86, illustratedby curve 98, has too high a RI to provide efficient TIR. One compatiblecomponent for decreasing the RI of light absorbing adhesive 86 is aperfluoroalkylsulfonamidoethyl acrylate, of whichN-methyl-perfluorobutylsulfonamidoethyl acrylate is an example. In someembodiments, light absorbing adhesive 86 contains at least about 1percent of a perfluoroalkylsulfonamidoethyl acrylate. In an exemplaryembodiment, light absorbing adhesive 86 contains at least about 10percent of a perfluoroalkylsulfonamidoethyl acrylate. In someembodiments, light absorbing adhesive 86 contains less than about 70percent of a perfluoroalkylsulfonamidoethyl acrylate. In an exemplaryembodiment, light absorbing adhesive 86 contains less than about 50percent of a perfluoroalkylsulfonamidoethyl acrylate.

Where light absorbing material 86 is photopolymerized, a suitablephotoinitiator is included; phenyl bis(2,4,6 trimethyl benzoyl)phosphine oxide photoinitiator and ∀,∀-diethoxyacetophenone (DEAP)photoinitiator are examples of suitable free radical photoinitiators. Insome embodiments, light absorbing adhesive 86 contains at least about0.5 percent of a photoinitiator. In an exemplary embodiment, lightabsorbing adhesive 86 contains about 1.0 percent of a photoinitiator. Insome embodiments, light absorbing adhesive 86 contains less than about 5percent of a photoinitiator. In other embodiments, a thermalpolymerization initiator or redox initiator is chosen.

In yet another embodiment, light absorbing adhesive 86 contains about54.4% amine terminated silicone polyurea (molecular weight 5,000 g/mole)reacted with isocyanatoethyl methacrylate; about 44.6% isobomylacrylate; and about 1.0% phenyl bis(2,4,6 trimethyl benzoyl) phosphineoxide photoinitiator. This formulation is coated on cured acrylatediffusive ribs 24 on one side and laminated to a shield 66 of Dupont 617primer polyester film on the other side. The layers are passed under a23.62 W/mm (600 W/in) Fusion Systems D lamp four times at 15.24 m/minute(50 feet/minute). The 180 degree peel force measured at a peel rate of127 mm/minute (5 inches/minute) by a model 3M90 slip/peel tester byInstrumentors, Inc. is about 73.2 kg/m (4.1 pounds/inch). The refractiveindex of the polymerized light absorbing adhesive formulation 86 isabout 1.45.

FIG. 9 illustrates yet another method by which a screen may bemanufactured. FIG. 9 shows one example of a co-extrusion process thatcan be used to produce microrib structure 20 instead of themicroreplication process 32 discussed with respect to FIG. 3. In oneexemplary embodiment shown in FIG. 9, co-extrusion die 104 is ahigh-temperature, high-pressure die for the simultaneous extrusion of atwo-layer film. In one embodiment, die 104 has an extruder orificediameter 105 of about 44.4 mm (1.75 inch) to about 50.8 mm (2 inches).The two-layer film is composed of material 106 to form base substrate 22and material 108 to form light diffusive ribs 24. In one embodiment,materials 106 and 108 are heated to about 66° C. (150° F.) and extrudedfrom die 104, which has a temperature of about 293° C. (560° F.). Eachmaterial 106 and 108 is isolated from the other until after they areextruded from die 104. After extrusion, the materials 106 and 108 arebrought into contact with each other, wherein at least material 108 isstill in a molten state.

The three-roll extrude-emboss technique shown in FIG. 9 uses a firstroll 110, a patterned second roll 112, and a third roll 114. In oneembodiment, each roll 110, 112 and 114 is about 0.43 m (17 inches) indiameter. First roll 110 and third roll 114 may be heated or chilled asrequired by the nature of the materials used to facilitate release ofthe materials from the roll surfaces. Materials 106 and 108 aresimultaneously extruded from die 104 onto patterned roll 112. In theillustrated embodiment, material 106 is extruded proximate nip roll 110and material 108 is extruded proximate patterned cast roll 112. In oneembodiment, first or nip roll 110 is heated to greater than or about 52°C. (125° F.) by running heated oil through interior 111 of roll 110, theoil being heated by an external heat source. In one exemplaryembodiment, nip roll 110 is formed of a material such as siliconerubber. Cast roll 112 is patterned on outer surface 117 to impart thedesired structures upon material 108 to result in light diffusive ribs24. In one exemplary embodiment, cast roll 112 is formed of a metal suchas chromium, nickel, titanium, or an alloy thereof. In one embodiment,cast roll 112 is heated to greater than or about 204° C. (400° F.), moreparticularly between about 252° C. (485° F.) and about 282° C. (540°F.), by running heated oil through interior 113 of roll 112, the oilbeing heated by an external heat source. Third or carrier roll 114 isgenerally heated or chilled by running oil or water through interior 115of roll 114 to assist in the release of microrib structure 20 from castroll 112. In one embodiment, carrier roll 114 is heated to greater thanor about 66° C. (150° F.) by running heated oil through the interior 115of roll 114, the oil being heated by an external heat source. In oneexemplary embodiment, carrier roll 114 has a smooth outer surface 119and is formed of a metal such as chromium, nickel, titanium, or an alloythereof.

In one embodiment, material 106 for forming base structure 22 is a lighttransmitting material such as a clear polymer such as polycarbonate,polyester, polyolefin, polypropylene, acrylic or vinyl, for example. Inone embodiment, material 108 for diffuser ribs 24 is a high refractiveindex polymer such as a modified acrylic, polycarbonate, polystyrene,polyester, polyolefin, polypropylene, or other optical polymer. It isparticularly suitable for material 108 to have a refractive indexgreater than or equal to about 1.50. Polycarbonate, with a RI of 1.59 isparticularly useful due to its high Tg, clarity and mechanicalproperties. In one embodiment, material 106 and material 108 arecompatible so that they physically bond at the interface therebetween tointegrate into a monolithic structure. This is achieved in one exemplaryembodiment by using the same polymer material for material 106 and 108,the difference being that material 108 incorporates light diffusingparticles into the polymer. In an alternate embodiment, material 106 andmaterial 108 can have different compositions, but they possess similarprocessing characteristics and bond to one another at their interface.

In one embodiment, nip roll 100 and cast roll 112 are in intimatecontact to provide high pressure onto materials 106 and 108 against castroll 112. This is especially important for materials with a high Tg suchas polycarbonate, which set up almost immediately upon exiting die 104.Carrier roll 114 need not be in intimate contact with cast roll 112; thepurpose of carrier or pull roll 114 is merely to take formed microribstructure 20 off cast roll 112. In one embodiment, each roll 110, 112and 114 rotates at about 3.6 m (12 feet) per minute, with adjacent rollsrotating in opposite directions.

In one embodiment, air bar 126 facilitates the release of structure 20off cast roll 112. Air bar 126 is a perforated cylinder which emitscooling air onto structure 20 just before the point of separation ofstructure 20 from cast roll 112. In one embodiment, air is supplied at620 kPa (90 psi) and ambient temperature. Materials 106 and 108 solidifyinto structure 20. In one embodiment, tensioning roll assembly 128 isused to provide the proper amount of tension on structure 20 as ittravels. Slitter 130 is provided to cut structure 20 to desired widths.Windup roll 132 winds up structure 20 for storage or later retrieval.

Other cast-emboss and extrude-emboss methods, for example, can also beused. The resulting microrib structure 20 can then be used in the methoddescribed with reference to FIGS. 6, 7A and 7B. In another embodiment,single layer extrusion can be used to extrude material 108 for forminglight diffusive ribs 24 onto a previously formed substrate 22. In thisembodiment, an input feeds substrate 22 so that material 108 in a moltenstate is extruded thereon and both materials are pressed together by niproll 10 so that material 108 is patterned by cast roll 112. Substrate 22and material 108 remain in intimate contact during the cooling phase.Referring back to FIG. 6, co-extrusion can also be used to extrude thedual layer of shield 66 and light absorbing adhesive 86. Suitablematerials for light absorbing adhesive 86 include those discussed withreference to FIG. 8, for example. In another exemplary embodiment,microrib structure 20 is filled with a black pigmented high melt flowPMMA light absorbing material 28 (see FIG. 2). In one exemplaryembodiment, shield 66 is a clear PMMA. This construction yields adesirably high refractive index difference of about 0.08 to 0.09 betweenlight absorbing material 28 and ribs 24.

FIGS. 10A-10C illustrate steps for manufacturing a screen in a thirdmethod. In this embodiment, light absorbing ribs 116 are formed uponshield 66 by a microreplication process or co-extrusion. (See FIGS. 3and 9 and related discussion). In an exemplary embodiment, ribs 116 forma plurality of cavities therebetween. In an exemplary embodiment, eachrib 116 has a base 121 and a plurality of walls 123 which narrow the rib116 as walls 123 extend from base 121. The cavities of structure 118between ribs 116 can then be filled with a material with a highrefractive index to form diffuser ribs 24. In an exemplary embodiment,the high refractive index material is discussed with respect to FIG. 1.Base substrate 22 can then be laid upon the filled structure to form arear projection screen element.

FIG. 10D illustrates an alternate step in a method for producing a rearprojection screen element. A layer of high refractive index material 120is provided adjacent base substrate 22 by a method such as coating orco-extrusion. The composite layer is laminated to structure 118 of FIG.10A so that the high refractive index material of layer 120 fills thespaces between light absorbing ribs 116 to produce light diffusing ribs24, ultimately resulting in the product shown in FIG. 10C.

Some advantages of the method illustrated in FIGS. 10A-10D include theability to use a thinner base structure 22 because its strength is notas crucial in the process. A thinner base structure 22 will cause feweroptical effects and allow for reduced materials usage.

FIG. 11 illustrates a third embodiment of a rear projection screen. Inone embodiment, overcoat layer 122 is made of a material which ismultifunctional to serve as a low refractive index component as well asa hard coat. In this way, the “TIR efficiency” is maintained, but thepotential need to laminate to a protective shield is eliminated sincethe material of overcoat layer 22 is scratch-resistant due to itsinherent hard properties. This combination of functions within onematerial further reduces material usage and costs. Suitable materialsfor overcoat layer 122 include hard coat materials incorporating apigment such as carbon black. In one embodiment, the pigment is used ina concentration between about 50 ppm (parts per million) and about20,000 ppm. In an exemplary embodiment, the concentration is greaterthan about 1,000 ppm and less than about 9,000 ppm. A concentration ofabout 3,000 ppm is particularly suitable, based on mass ratios of thecarbon black material to the hard coat material.

One suitable hard coat material is disclosed in U.S. Pat. No. 5,104,929to Bilkadi, hereby incorporated by reference. Bilkadi teaches aphotocurable abrasion resistant coating including colloidal silicondioxide particles dispersed in ethylenically unsaturated aliphaticand/or cycloaliphatic monomers that are substituted by a protic group.In particular, the coating composition curable to an abrasion andweather resistant coating includes a dispersion of colloidal silicondioxide particles of diameters less than about 100 nanometers in aprotic group-substituted ester or amide of acrylic or methacrylic acid.

Another suitable hard coat material is disclosed in U.S. Pat. No.5,633,049 to Bilkadi, hereby incorporated by reference. Bilkadi teachesan acid- and abrasion-resistant coating prepared from a silica-freeprotective coating precursor composition including a multifunctionalethylenically unsaturated ester of acrylic acid, a multifunctionalethylenically unsaturated ester of methacrylic acid, or a combinationthereof; and an acrylamide.

Other hard coat materials include room-temperature curing siliconeresins derived from functionalized silane monomers; coatings derivedfrom hydrolyzable silanes; polymers derived from a combination ofacryloxy functional silanes and polyfunctional acrylate monomers;polymers such as acrylic with colloidal silica; and polymerized acrylateor methacrylate functionalities on a monomer, oligomer or resin; forexample.

FIG. 12 is a side elevation view of another embodiment of a rearprojection screen. Embedded microstructured film 27 is provided with ahard coat 124 to protect the film against scratching and other damage.Hard coat 124 may be applied by spraying, dipping, or roll coating, forexample. This process eliminates the need for a separate protectiveshield 66 and the lamination process illustrated in FIG. 5.

Although the present invention has been described with reference toexemplary embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention. For example, while particular shapes forlight diffusive and light absorbing structures are illustrated, it iscontemplated that the structures may be formed in different shapes,incorporating additional or different planes or angles, additionaledges, and curved surfaces. It is further noted that the light diffusivestructures on a particular substrate need not all be of the same heightor shape, for example. Similarly, the light absorbing structures on aparticular substrate need not all be of the same height or shape, forexample. Moreover, components of the materials and processes describedtherein are combinable in numerous ways; only a few of thosepossibilities have been specifically described by way of example,although all are regarded to be within the scope of the invention.

For example, in a first embodiment, light diffusive ribs 24 are formedfrom an acrylated aliphatic urethane oligomer resin with an addition ofabout 0.1 pph (parts per hundred) to about 10 pph2-hydroxy-2-methyl-1-phenyl-1-propanone photoinitiator; in an exemplaryembodiment, about 2 pph photoinitiator is used. In a second embodiment,light diffusive ribs 24 are formed from an ethoxylated bisphenol Adiacrylate resin with an addition of about 0.1 pph to about 10 pph2-hydroxy-2-methyl-1-phenyl-1-propanone photoinitiator; in an exemplaryembodiment, about 2 pph photoinitiator is used.

In a third embodiment, light diffusive ribs 24 are formed from a resincontaining about 90% to about 95% acrylated aliphatic urethane oligomerand about 5% to about 10% ethoxylated bisphenol A diacrylate with anaddition of about 0.1 pph to about 10 pph2-hydroxy-2-methyl-1-phenyl-1-propanone photoinitiator; in an exemplaryembodiment, about 2 pph photoinitiator is used. The acrylated aliphaticurethane oligomer possesses high strength properties while theethoxylated bisphenol A diacrylate possesses desirable viscosity and RIcharacteristics.

In a fourth embodiment, light diffusive ribs 24 are formed from a resincontaining about 20% to about 95% (more preferably about 50% to about90%) ethoxylated bisphenol A diacrylate and about 5% to about 80% (morepreferably about 10% to about 50%) acrylated epoxy oligomer with anaddition of about 0.1 pph to about 10 pph2-hydroxy-2-methyl-1-phenyl-1-propanone photoinitiator; in an exemplaryembodiment, about 2 pph photoinitiator is used. The acrylated epoxyoligomer possesses desirable viscosity and RI characteristics.

In a fifth embodiment, light diffusive ribs 24 are formed from a resincontaining about 10% to about 90% (more preferably about 25% to about75%) acrylated aliphatic urethane oligomer and about 10% to about 90%(more preferably about 25% to about 75%) acrylated epoxy oligomer withan addition of about 0.1 pph to about 10 pph2-hydroxy-2-methyl-1-phenyl-1-propanone photoinitiator; in an exemplaryembodiment, about 2 pph photoinitiator is used.

In a sixth embodiment, light diffusive ribs 24 are formed from a resincontaining about 10% to about 80% (more preferably about 20% to about70%) acrylated aliphatic urethane oligomer; about 10% to about 70% (morepreferably about 20% to about 60%) ethoxylated bisphenol A diacrylateand about 5% to about 65% (more preferably about 10% to about 50%)acrylated epoxy oligomer with an addition of about 0.1 pph to about 10pph 2-hydroxy-2-methyl-1-phenyl-1-propanone photoinitiator; in anexemplary embodiment, about 2 pph photoinitiator is used.

In a seventh embodiment, light diffusive ribs 24 are formed from a resincontaining about 30% to about 70% (more preferably about 50%) acrylatedaliphatic urethane oligomer and about 30% to about 70% (more preferablyabout 50%) acrylated aromatic urethane oligomer with an addition ofabout 0.1 pph to about 10 pph 2-hydroxy-2-methyl-1-phenyl-1-propanonephotoinitiator; in an exemplary embodiment, about 2 pph photoinitiatoris used. The acrylated aromatic urethane oligomer possesses desirableviscosity and RI characteristics.

In an eighth embodiment, light diffusive ribs 24 are formed from a resincontaining about 30% to about 90% (more preferably about 50% to about75%) acrylated aliphatic urethane oligomer and about 10% to about 70%(more preferably about 25% to about 50%) 2-(1-naphthyloxy)-ethylacrylate with an addition of about 0.1 pph to about 10 pph2-hydroxy-2-methyl-1-phenyl-1-propanone photoinitiator; in an exemplaryembodiment, about 2 pph photoinitiator is used.

In a ninth embodiment, light diffusive ribs 24 are formed from a resincontaining about 40% to about 80% (more preferably about 60%) acrylatedaliphatic urethane oligomer; about 10% to about 30% (more preferablyabout 20%) ethoxylated bisphenol A diacrylate and about 10% to about 30%(more preferably about 20%) 2-(1-naphthyloxy)-ethyl acrylate with anaddition of about 0.1 pph to about 10 pph2-hydroxy-2-methyl-1-phenyl-1-propanone photoinitiator; in an exemplaryembodiment, about 2 pph photoinitiator is used.

In a tenth embodiment, light diffusive ribs 24 are formed from a resincontaining about 30% to about 70% (more preferably about 50%) acrylatedaliphatic urethane oligomer; about 10% to about 40% (more preferablyabout 25%) acrylated epoxy oligomer and about 10% to about 40% (morepreferably about 25%) 2-(1-naphthyloxy)-ethyl acrylate with an additionof about 0.1 pph to about 10 pph 2-hydroxy-2-methyl-1-phenyl-1-propanonephotoinitiator; in an exemplary embodiment, about 2 pph photoinitiatoris used.

In an eleventh embodiment, light diffusive ribs 24 are formed from aresin containing about 30% to about 70% (more preferably about 50% toabout 60%) acrylated aliphatic urethane oligomer; about 5% to about 30%(more preferably about 6% to about 15%) ethoxylated bisphenol Adiacrylate; about 5% to about 40% (more preferably about 15% to about30%) acrylated epoxy oligomer; and about 5% to about 45% (morepreferably about 15% to about 35%) 2-(1-naphthyloxy)-ethyl acrylate withan addition of about 0.1 pph to about 10 pph2-hydroxy-2-methyl-1-phenyl-1-propanone photoinitiator; in an exemplaryembodiment, about 2 pph photoinitiator is used.

In a twelfth embodiment, light diffusive ribs 24 are formed from a resincontaining about 30% to about 90% (more preferably about 50% to about80%) acrylated aliphatic urethane oligomer; about 5% to about 25% (morepreferably about 6.7% to about 16.7%) ethoxylated bisphenol Adiacrylate; and about 5% to about 45% (more preferably about 10% toabout 33.3%) 2(2,4,6-tribromophenoxy)ethyl acrylate with an addition ofabout 0.1 pph to about 10 pph 2-hydroxy-2-methyl-1-phenyl-1-propanonephotoinitiator; in an exemplary embodiment, about 2 pph photoinitiatoris used. The 2(2,4,6-tribromophenoxy)ethyl acrylate increases the RI ofthe resin.

In a thirteenth embodiment, light diffusive ribs 24 are formed from aresin containing about 30% to about 90% (more preferably about 50% toabout 70%) acrylated aliphatic urethane oligomer; about 5% to about 20%(more preferably about 6% to about 13.3%) ethoxylated bisphenol Adiacrylate; about 5% to about 35% (more preferably about 10% to about25%) 2-(1-naphthyloxy)-ethyl acrylate; and about 5% to about 35% (morepreferably about 10% to about 26.7%) 2(2,4,6-tribromophenoxy)ethylacrylate with an addition of about 0.1 pph to about 10 pph2-hydroxy-2-methyl-1-phenyl-1-propanone photoinitiator; in an exemplaryembodiment, about 2 pph photoinitiator is used.

In a fourteenth embodiment, light diffusive ribs 24 are formed from aresin containing about 30% to about 70% (more preferably about 50%)acrylated aliphatic urethane oligomer; about 5% to about 35% (morepreferably about 16.7% to about 25%) ethoxylated bisphenol A diacrylate;and about 10% to about 45% (more preferably about 25% to about 33.3%)other RI modification materials (such as2,2-bis(3,5-dibromo-4(acryloyloxy-2-hydroxypropoxy)phenyl)propane;2,4-dibromo-6-sec-butyl-phenyl acrylate;2-(naphthalen-2-ylsulfonyl)-ethyl acrylate; and polystyrene macromers,for example) with an addition of about 0.1 pph to about 10 pph2-hydroxy-2-methyl-1-phenyl-1-propanone photoinitiator; in an exemplaryembodiment, about 2 pph photoinitiator is used.

In a fifteenth embodiment, light diffusive ribs 24 are formed from aresin containing about 30% to about 70% (more preferably about 40% toabout 50%) acrylated aliphatic urethane oligomer; about 15% to about 45%(more preferably about 25% to about 33.3%) 2-(1-naphthyloxy)-ethylacrylate; and about 5% to about 45% (more preferably about 16.7% toabout 30%) other RI modification materials with an addition of about 0.1pph to about 10 pph 2-hydroxy-2-methyl-1-phenyl-1-propanonephotoinitiator; in an exemplary embodiment, about 2 pph photoinitiatoris used.

In a sixteenth embodiment, light diffusive ribs 24 are formed from aresin containing about 40% to about 75% (more preferably about 60%)acrylated aliphatic urethane oligomer; about 5% to about 15% (morepreferably about 6.7%) ethoxylated bisphenol A diacrylate; about 10% toabout 30% (more preferably about 20%) 2-(1-naphthyloxy)-ethyl acrylate;and about 5% to about 30% (more preferably about 13.3%) other RImodification materials with an addition of about 0.1 pph to about 10 pph2-hydroxy-2-methyl-1-phenyl-1-propanone photoinitiator; in an exemplaryembodiment, about 2 pph photoinitiator is used.

In a seventeenth embodiment, light diffusive ribs 24 are formed from aresin containing about 40% to about 75% (more preferably about 60%)acrylated aliphatic urethane oligomer; about 5% to about 15% (morepreferably about 5.5% to about 6.7%) ethoxylated bisphenol A diacrylate;about 5% to about 25% (more preferably about 13.3% to about 15%)2(2,4,6-tribromophenoxy)ethyl acrylate; and about 10% to about 30% (morepreferably about 20%) other RI modification materials with an additionof about 0.1 pph to about 10 pph 2-hydroxy-2-methyl-1-phenyl-1-propanonephotoinitiator; in an exemplary embodiment, about 2 pph photoinitiatoris used.

The loading of the light scattering particles within the resin forforming light diffusive ribs 24 is chosen to control optical propertiessuch as gain and view angle of the screen. In an exemplary embodiment,the light scattering particles are loaded in the resin in aconcentration of about 0.5% to about 30%, more preferably about 2% toabout 20%, and even more preferably about 4% to about 15%. In anexemplary embodiment, the light scattering particles preferably have ahigher RI than the resin in which the particles are dispersed.Generally, as the RI of the resin increases, the loading of the lightscattering particles must also increase to maintain a given peak gainvalue. Moreover, as the surface texture of the back surface of the basesubstrate 22 becomes less matte, the loading of the light scatteringparticles must also generally increase to maintain a given peak gainvalue. Suitable materials for the light scattering particles include acopolymer of ethyl methacrylate and polystyrene; a copolymer of methylmethacrylate and polystyrene; and polystyrene, for example.

1. An optical material comprising a composition of aperfluoroalkylsulfonamidoalkyl acrylate, an aliphatic urethane acrylateoligomer, and an acrylate monomer.
 2. The optical material of claim 1,wherein the composition comprises a copolymer.
 3. The optical materialof claim 1 being curable by light.
 4. The optical material of claim 3,wherein the light is ultraviolet.
 5. The optical material of claim 1being an adhesive.
 6. The optical material of claim 1 being a pressuresensitive adhesive.
 7. The optical material of claim 1, wherein theindex of refraction of the composition is less than about 1.5.
 8. Theoptical material of claim 1 further comprising a light absorbingpigment.
 9. A film comprising: a first layer; a second layer disposed onthe first layer; a polymerized composition disposed between the firstand second layers for attaching the first layer to the second layer, thecomposition comprising an aliphatic urethane acrylate oligomer, anacrylate monomer, and a perfluoroalkylsulfonamidoalkyl acrylate.
 10. Thefilm of claim 9, wherein the perfluoroalkylsulfonamidoalkyl acrylate isa perfluoroalkylsulfonamideoethyl acrylate.
 11. The film of claim 9,wherein the first layer is structured.
 12. A projection screencomprising the film of claim
 9. 13. The projection screen of claim 12being a front projection screen.
 14. The projection screen of claim 12being a rear projection screen.
 15. The projection screen of claim 12dispersing light by total internal reflection.
 16. A film comprising: asubstrate; and a plurality of structures disposed on the substrate, eachof the plurality of structures being made by polymerization of acomposition, the composition comprising an aliphatic urethane acrylateoligomer, an acrylate monomer, and a perfluoroalkylsulfonamidoalkylacrylate.